Which colours make us feel happy? And which sad? As last year (Simmons, VSS 2006) we approached the colour-emotion relationship issue systematically by running a series of experiments in which participants were presented with an array of three coloured patches, chosen from a limited set of ten, on a neutral gray background. The colour set was chosen based on pilot experiments and the colours were specified using CIE coordinates. A series of four experiments were performed using 39 participants. In the first two, participants were asked to choose which of the three colours made them feel the happiest; in the second two, which of the three made them feel most sad. All possible three-colour combinations from each set were tested, allowing a happiness and sadness hierarchy to be established for each colour set. For the happy-sad dimension there was a clear effect of saturation, with the more saturated colours tending to evoke more “happy” responses and less “sad” responses. The saddest colours in a given set were always the least saturated. However, hue was also found to be important for happiness in that the most happy responses were reported for a sunny yellow in both test sets. Taken together with the results from Simmons (2006), we suggest that there are four universal factors which strongly influence emotional responses to colour. The first is an arousal component related to the perceived depth of the colour (far-away things tend to be bluer and grayer). The second is a pleasure component related to the saturation of the colour. The third is an aversion to yellow-green and brown due to unpleasant associations, whilst the fourth is a strong affinity to sunny yellows due to associations with fine weather. These rules are largely consistent with extant data on colour and emotions and inform current theories of visual aesthetics.